1. Field of the Invention
The present invention relates to an insulated wire and an insulated cable, more particularly, to an insulated wire and an insulated cable with excellent oil resistance property and flexibility using a thermoplastic elastomer.
Further, the present invention relates to a non-halogen flame retardant wire and a non-halogen flame retardant cable, more particularly, to a non-halogen (halogen free) flame retardant wire and a non-halogen (halogen free) flame retardant cable with excellent oil resistance property and flame retardant property.
2. Related Art
In recent years, as an insulator to be coated on the electric wire or cable, an insulator comprising a thermoplastic elastomer has been used. It is because that the thermoplastic elastomer is advantageous as compared to a rubber since the thermoplastic elastomer can be used at a high temperature without requiring a crosslinking process. The thermoplastic elastomer is further advantageous in that it is possible to supply the electric wire or cable with low cost and high recyclable property, since the cross linking process is not required.
For the electric wires and cables, heat resistance property, oil resistance property, flexibility, wiring property, and the like are required. Accordingly, it is impossible to satisfy these properties by a single kind of polyolefin constituting the thermoplastic elastomer that is a material of the insulator for the electric wires and cables. Namely, when using only crystalline polyolefin, thermoplastic elastomer thus obtained is excellent in the heat resistance property and the oil resistance property. However, it is impossible to obtain the flexibility equivalent to that of conventional soft PVC. On the other hand, when using only amorphous polyolefin, the obtained thermoplastic elastomer is excellent in the flexibility. However, it is impossible to obtain the heat resistance property and the oil resistance property.
Therefore, a blended composition of different kinds of polyolefins having different properties such as the crystalline polyolefin and the amorphous polyolefin is used for obtaining a thermoplastic elastomer excellent in the heat resistance property, the oil resistance property, and the flexibility.
Blending techniques for the thermoplastic elastomer are roughly classified into (1) simple blending type, (2) dynamic crosslinking type, and (3) reactor blending type.
(1) The simple blending type is to mix two or more kinds of elastomers after mechanically shearing the elastomers by a mixer. (2) The dynamic crosslinking type is to add a crosslinking process when blending the elastomer serving as a disperse phase with the elastomer serving as a matrix phase, in order to agglomeration of the disperse phase. (3) The reactor blending type is to blend resin components generated at respective stages in a reactor at time of polymerization when manufacturing by the multi-stage polymerization.
In general, when the polyolefins having different characteristics are blended with each other, the blended composition has a sea-island structure wherein one polyolefin serves as a sea phase and another polyolefin serves as an island phase. At this time, compatibility of advantages of the polyolefins having different characteristics is increased in accordance with reduction in diameter of the disperse phase serving as the island phase. However, mutual solubility in blending the polyolefins having different characteristics is low, so that it was difficult to miniaturize the disperse phase.
For example, (1) simple blended type thermoplastic elastomer has the sea-island structure, in which the disperse phase is largely dispersed in the matrix phase. In (2) dynamically crosslinked type thermoplastic elastomer, the agglomeration of the disperse phase is prevented and the diameter of the disperse phase is reduced, by adding the crosslinking process. However, the disperse phase is dispersed largely in the matrix phase, so that the properties of the polyolefin serving as the matrix phase are dominant. Therefore, it is difficult to utilize the properties of the polyolefin serving as the disperse phase. Since (3) reactor blended type thermoplastic elastomer is manufactured by the multi-stage polymerization, it is possible to finely disperse the amorphous polyolefin serving as the disperse phase in the crystalline polyolefin serving as the matrix phase, compared to the (1) simple blended type thermoplastic elastomer and the (2) dynamically crosslinked type thermoplastic elastomer. However, it was difficult to disperse the amorphous polyolefin so finely that the oil resistance property of the crystalline polyolefin and the flexibility of the amorphous polyolefin in the blended composition of a conventional reactor blended type thermoplastic elastomer.
In particular, for electric wires and cables, the flame retardant property and the oil resistance property are required. Accordingly, a crosslinked chloroprene rubber has been used as the insulator to be coated on the electric wires and the cables. It is because that the crosslinked chloroprene rubber contains high polarity chlorine in its composition, and is excellent in the oil resistance property particularly in the mineral oil resistance property. Further, the crosslinked chloroprene rubber is excellent in the flame retardant property, since the crosslinked chloroprene rubber discharges the chlorine to suppress the inflammation of the insulator. Therefore, the crosslinked chloroprene rubber has been used as an oil resistance and flame retardant rubber.
From the point of view of escalation in interest with respect to the environment in recent years, the electric wires and cables coated with insulator comprising a non-halogen composition that does not discharge a harmful halogen gas to an atmosphere in combustion has been requested. However, since the crosslinked chloroprene rubber is crosslinked and further contains the chlorine, the crosslinked chloroprene rubber has not been used as a non-halogen material and a recyclable material.
Therefore, as an insulator to be coated on the electric wire or cable, an insulator comprising a non-halogen type thermoplastic elastomer has been used to provide the insulator with the halogen free property and the recyclable property. It is because that the non-halogen type thermoplastic elastomer is advantageous as compared to the crosslinked chloroprene rubber since the non-halogen type thermoplastic elastomer can be used at a high temperature without requiring a crosslinking process. The non-halogen type thermoplastic elastomer is further advantageous in that it is possible to supply the electric wire or cable with low cost and high recyclable property, since the cross linking process is not required.
As a related art, Japanese patent laid-open No. 6-25367 discloses that the olefin-based composition using the reactor blending type (3) is excellent in the flexibility. Japanese patent laid-open No. 2006-241225 discloses the thermoplastic elastomer excellent in the flexibility, the damage resistance property, and the tensile property, which is applicable to the insulator for the electric wire. Japanese publication No. 2006-505685 of translation for International publication discloses the thermoplastic olefin-based composition excellent in the heat resistance property and the tensile strength that is applied to the insulator for the electric wire. Japanese patent laid-open No. 2006-505685 discloses the thermoplastic olefin-based composition excellent in the heat resistance property and the tensile strength, which is applicable to the insulator for the electric wire.